The present invention relates to a method for selecting a wavelength to affect the etching processing results, from light emission data measured during plasma etching processing (hereafter called etching processing) in etching devices that machine the semiconductor wafer by using plasma.
In order to achieve a microscopic shape such as for a semiconductor device formed over a wafer, plasma is utilized to ionize a substance, and by using the effect from that substance, (reaction with wafer surface) etching is performed to remove a substance over the wafer. There are a variety of substances for ionizing and there are also many types and forms of substances over the wafer material used according to the required product performance.
Moreover, in order to form a shape over the wafer, an organic substance resist is coated over the wafer, a shape is formed by photolithography, and etching performed. A substance is also placed whose reaction speed can be adjusted in order to obtain a specified shape. A variety of types and forms of substances that react with each other can be placed within the chamber for performing the etching process.
The ionizing phenomenon implemented by plasma is accompanied by a light emission phenomenon, so etching devices that utilize plasma in the etching process include a spectroscope (OES: Optical Emission Spectroscope) capable of monitoring the plasma emission status.
Data measured by a spectroscope is hereafter called OES data.
The OES data contains two dimensional spatial and temporal elements and expresses the emission intensity values respectively measured at each time and wavelength.
The light emission intensity values fluctuate according to the state of the etching process so the etching process is controlled by using the OES data. In one example of this control, the etching process is terminated or the inflow gas quantity is reduced when a specified wavelength value among the OES data has exceeded the threshold.
Japanese Unexamined Patent Application Publication No. Hei9 (1997)-306894 discloses a method for identifying the wavelength used for controlling the etching from the OES data.
Japanese Unexamined Patent Application Publication No. Hei9 (1997)-306894 discloses a method to analyze the emitted light occurring along with the plasma processing by the plasma device, and automatically setting an optimal wavelength for detecting a pre-established endpoint prior to executing plasma processing based on fluctuations over accumulated time in the light emission intensity on the specified wavelength. More specifically, a method is disclosed for setting a wavelength whose maximum value is the differential detected by an intensity differential detector circuit, as the optimal wavelength.